The present invention relates to a method and system for selectively distributing reactant precursors to separate locations on a receiver. Particularly, the invention relates to a method and system for preparing a combinatorial library of luminescence material precursors for screening by combinatorial high throughput screening (CHTS).
Luminescence materials, also called phosphors, can convert a certain type of energy into electromagnetic radiation over thermal radiation. A phosphor is usually composed of a host lattice doped with fluorescent-active elements (activator) present in up to a few mole %. Phosphors have been widely used in fluorescent lamps, displays, scintillation, etc. Although the search for advanced phosphors started about a century ago, the new photonic technologies, including mercury-free fluorescent lamps, various flat panel displays, computed tomography (CT), etc., require new phosphors with advanced properties: These include high quantum efficiency, good absorption of the excitation energy, adequate color coordinate, long lifetime, and low cost.
The discovery of advanced oxide phosphors with multiple superior qualities for display applications remains a difficult problem. The specific spectral properties, absorption, quantum efficiencies, and lumen maintenance depend on complex interactions between the excitation source, host lattice, structural defects, and fluorescent dopants. Luminescence properties are highly sensitive to the changes in dopant composition, host stoichiometry, and processing conditions. Consequently, the identification of phosphors that are ideally suited to the requirements of a given display technology is highly empirical.
Combinatorial chemistry techniques have been applied to search for new phosphors in thin film form or powder form. Sun, Ted X., Biotechnology and Bioengineering Combinatorial Chemistry, 61, 4 (1998/1999) shows that a combination of a thin-film deposition and a masking strategy can be used to generate a thin film xe2x80x9cspatially addressable library,xe2x80x9d where each sample precursor in the library is formed from a multiple-layer. Following deposition of precursor layers, interdiffusion of the layers can be effected by a thermal annealing step and the phosphors synthesized in a following high temperature step.
However, most phosphors used in industry are in powder form. The thin-film techniques result in libraries of materials that are substantially two-dimensional as opposed to a three dimensional powder form. The substantially two dimensional libraries cannot replicate the industrial powder form of phosphors and the results of testing the thin-film-created libraries can not always be extrapolated to industrial conditions.
In the synthesis of phosphor libraries in powder form, solutions of elemental precursors are dispensed using an automatic liquid injector with accurate control of volume. In this process, elemental precursors mix on a molecular scale prior to coprecipitation and high temperature synthesis. For example, in Xiang et al., U.S. Pat. No. 6,048,469, libraries of phosphor materials are generated using dispensers of a multi-jet delivery system. In this process, solutions of precursors are deposited by a xe2x80x9cdroplet-on-demandxe2x80x9d ink jet system operated with a piezoelectric disc, which squeezes a drop of liquid when pulsed with an electric signal.
However, a multi-jet delivery system cannot handle viscose solutions or gels, gels or solid suspensions that are the necessary precursors of phosphor materials. Materials of a viscosity greater than about 1 centipoise tend to clog the orifices of multi-jet type systems. Some of the precursors are so viscous that they cannot be delivered through the ink-jet nozzle. Additionally, known multi-jet systems are designed for discovery processing of relatively benign materials. Many of the phosphor library precursors must be delivered as highly acidic solutions. The viscous solutions cannot be delivered through the orifices of the multi-jet type systems and the deleterious acidic phosphor solutions cause deterioration of known multi-jet delivery system structures.
There is a need for a method and apparatus to produce a precursor phosphor library that emulates forms of industrially used phosphors. Additionally, there is a need for a method and apparatus that will resist deteriorating effects of various phosphor precursor compositions.
The invention meets these needs by providing a method and apparatus to deliver a library of precursor phosphor materials from solutions and gels of particle-sized materials and by providing a method and apparatus that resists the effects of deleterious precursor phosphor materials.
In a first embodiment, a method comprises positively displacing a first luminescence material precursor from a dispenser to a first position of an array, displacing a second luminescence material precursor from a dispenser mechanism to a second position of an array and simultaneously reacting the first and second precursors to produce a library of candidate luminescence materials.
In another embodiment, the invention relates to a method, comprising establishing a combinatorial library of precursor luminescence materials, effecting parallel reaction of said library to produce a library of candidate luminescence materials and evaluating each candidate material to select a best material from among said candidate library.
In another embodiment, the invention relates to a combinatorial high throughput screening liquid dispenser assembly. The assembly comprises a battery of positive displacement driven dispensers for dispensing solutions of precursor luminescence materials, an array plate with wells to receive dispensed solution from the dispenser, a robotic positioning table supporting the array plate to position wells beneath respective dispensers and a controller to control dispensing of the solutions and positioning of the plate.
In still another embodiment, the invention relates to a combinatorial high throughput screening system. The system includes the dispensing assembly, a furnace to heat treat solutions of precursor luminescence materials in the wells and an evaluator to evaluate luminescence materials from the precursors.